My apologies for having posted prematurely before. I haven't found my notes
(at this point I won't take the time to look for them anymore), but I quickly
worked up the following. To my relief, it is clear that what I remembered is
correct. There is no reson to doubt the pedigree as it was presented in the
previous posts, correcting one birthdate. The following is what I can prove
from original sources:

1. Oliver St. John, said to be of Fonmon, Glamorgan. I have not had time to
check yet, but he may be son of Alexander St. John of Instow, co. Devon, who
was living in 1340. Alexander is said to have married Elizabeth, daughter of
Sir Henry Umphreville of Penmark, Glamorgan. There are earlier conflicting
pedigrees which make Sir John St. John father of Alexander, and make that Sir
John son of William St. John of Fonmon, who is supposed to be a younger son of
Sir Robert de St. John of Basing [d. Mar. 1266/7].
The line from Sir Robert back five more generations to Hugh de Port is
certain, but I have not seen evidence for the father and grandfather of
Alexander yet, so the connection is still tentative.
Oliver St. John held lands in cos. Devon and Somerset, and died in August
1374. He married, by 19 June 1335 (the date of her proof of age), Elizabeth de
Luccombe, b. 1320 at Stockleigh Luccombe, co. Devon, daughter and eventual heir
of Hugh de Luccombe. They had two sons, (1) John St. John (see below) and (2)
Henry St. John.

2. John St. John, born possibly 1340 (his mother was only 14-15 in 1335), of
Fonmon, Glamorgan, and East Luccombe, Somerset. His brother Henry unlawfully
entered and took possession of his inheritance after his death. John married
Elizabeth, daughter and coheir of Agnes de la Bere of Coity (Glamorgan) and
Watertown.
I assume (but I need to check my files again) from the chronology that
Agnes de la Bere of Coity is the Agnes who was wife of Sir John de la Bere.
Agnes was one of four daughters and eventual heirs (after the deaths of Sir
Gilbert and Richard de Turberville and their heirs) of Payne and Wenllian de
Turberville of Coity, Glamorgan. Payne, dead by 1318/19, had served as
Sheriff of Glamorgan in 1315 and appointed keeper of the castles and lands of
Gilbert de Clare "late" Earl of Gloucester, and Cardiff Castle during royal
pleasure. A younger sister, Sarah de Turberville, married Gilbert Gamage, and
it was through their family that Coity eventually descended. The Cartae of
Glamorgan document that an earlier Gilbert de Turbervill had married Matilda,
daughter of Morgan Chan. They were parents of Richard de Turbervile, father of
Payne de Turberville (above). Back to the main line:

3. Sir John de St. John, born after 1360, but before 1363, at Salisbury,
Wilts., died 26 Dec. 1424. He was knighted by 1388. He married, by Easter
1395, Isabel/Elizabeth, widow of Sir John de Paveley. Sir John became a member
of Richard II's household. Sir John proved his worth and held many positions
in Wales and England, and was even appointed Mayor of Bordeaux by Henry V.

4. Sir Oliver St. John, born by 1398, was aged 26 at his father's death.
Oliver's witnessed the conveyance of the manor of Llanfair, Glamorgan, and was
mentioned in other Welsh records. As his father was such a prominent member of
the royal household, it is no wonder that he was married, as her first husband,
to Margaret Beauchamp (the "de" in surnames was generally dropped about 1400),
heir of the Barony of Bletsoe. Margaret was born about 1409-10 (aged 11 in
1420-1), and DIED IN 1482-3. Her first husband, Sir Oliver, died in 1437.
As previously stated, Margaret married, second, John Beaufort, Duke of
Somerset, by whom she was grandmother of Henry VII. It was probably because of
this close connection with the House of Tudor that her eldest son and heir was
made a Knight of the Bath after Henry VII ascended the throne.

5. SIr John St. John, Knight of the Bath, was found to be aged forty or more
AT THE DEATH OF HIS MOTHER in 1482-3. As his father died in 1437, he must have
been born shortly before his father's death. He married Alice Bradshaw,
daughter of Thomas Bradshaw of the Haugh, Lancashire. Bartrum states that he
married (2) Elizabeth, daughter of Wililam Fawr, son of Sir David Mathew of
Llandaf Court. I have no reason to doubt this, but all children are indicated
to be by the first wife, Alice. Strangely, no inquisition or will has been
found for this Sir John.
Sir John and Alice (Bradshaw) St. John also had a daughter, Anne St. John,
who married, by 1493 (the birth year of their son and heir), Henry, Lord
Clifford, "the Shepherd Lord."

6. Sir John St. John, Knight of the Bath, of Bletsoe, Bedfordshire, was
probably born by 1460 (certainly several years earlier than 1475). He married
Sybil, daughter of Rhys ap Morgan ap Jenkin. (I have to check Bartrum again,
as I think he said Sir John married Margared v. Morgan ap Jenkin. Morgan ap
Jenkin had married [2] Margared, daughter of Sir David Mathew of Llandaf Court
[above].)
Sir John St. John died in 1525, leaving a will proved in the PCC. His
inquisition post mortem found that his son and heir, John, was aged 30 and
more. A daughter Alice had married, before 1505, Henry Parker, Lord Morley.
As their son and heir Henry Parker was a page of the Chamber to Henry VIII in
1516, Alice was clearly several years older than her brother John (b. 1495),
which pushes her parent's marriage date back before 1485. This is important as
it eliminates any possiblity of an extra generation between the Sir John St.
John who was son of Margaret Beauchamp and Sir John who died in 1525.

7. Sir John St. John, born in or before 1495, died in 1558. His monumental
inscription says he was raised by Margaret Beaufort (d. 1509). He married
Margaret Walgrave by 1521, and was father of Oliver St. John, 1st Lord St. John
of Bletsoe (d. 1581-2).
I hope this in some way makes up for the confusion of my previous posts.